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PubMed2000

Genetically modified plants - the debate continues.

The debate about the potential risks and benefits of genetically modified organisms (GMOs) has hit the headlines over the past few months. The polarization of much of the debate obscures what really constitutes ecological risk, and what methods we can apply to identify and quantify those risks. Ecological science has much to offer in this respect, including ecological theory, manipulative experiments, the application of molecular tools and the interpretation of observational data from conventional agriculture. In the current heated debate, it is perhaps belief in the scientific method, above all else, that needs to be promoted and discussed.

Journal Article↗

PubMed1999

Plants genetically modified to produce N-acylhomoserine lactones communicate with bacteria.

N-acylhomoserine lactones (AHLs) play a critical role in plant/microbe interactions. The AHL, N-(3-oxohexanoyl)-L-homoserine lactone (OHHL), induces exoenzymes that degrade the plant cell wall by the pathogenic bacterium Erwinia carotovora. Conversely, the antifungal activity of the biocontrol bacterium Pseudomonas aureofaciens 30-84 is due (at least in part) to phenazine antibiotics whose synthesis is regulated by N-hexanoylhomoserine lactone (HHL). Targeting the product of an AHL synthase gene (yenI) from Yersinia enterocolitica to the chloroplasts of transgenic tobacco plants caused the synthesis in plants of the cognate AHL signaling molecules (OHHL and HHL). The AHLs produced by the transgenic plants were sufficient to induce target gene expression in several recombinant bacterial AHL biosensors and to restore biocontrol activity to an HHL-deficient P. aureofaciens strain. In addition, pathogenicity was restored to an E. carotovora strain rendered avirulent as a consequence of a mutation in the OHHL synthase gene, carI. The ability to generate bacterial quorum-sensing signaling molecules in the plant offers novel opportunities for disease control and for manipulating plant/microbe interactions.

Bacterial Proteins↗

PubMed2004

Potato plants genetically modified to produce N-acylhomoserine lactones increase susceptibility to soft rot erwiniae.

Many gram-negative bacteria employ N-acylhomoserine lactones (AHL) to regulate diverse physiological processes in concert with cell population density (quorum sensing [QS]). In the plant pathogen Erwinia carotovora, the AHL synthesized via the carI/expI genes are responsible for regulating the production of secreted plant cell wall-degrading exoenzymes and the antibiotic carbapen-3-em carboxylic acid. We have previously shown that targeting the product of an AHL synthase gene (yenI) from Yersinia enterocolitica to the chloroplasts of transgenic tobacco plants caused the synthesis in planta of the cognate AHL signaling molecules N-(3-oxohexanoyl)-L-homoserine lactone (3-oxo-C6-HSL) and N-hexanoylhomoserine lactone (C6-HSL), which in turn, were able to complement a carI-QS mutant. In the present study, we demonstrate that transgenic potato plants containing the yenI gene are also able to express AHL and that the presence and level of these AHL in the plant increases susceptibility to infection by E. carotovora. Susceptibility is further affected by both the bacterial level and the plant tissue under investigation.

Carboxylic Ester Hydrolases↗

PubMed2005

Effects of plants genetically modified for insect resistance on nontarget organisms.

Insect resistance, based on Bacillus thuringiensis (Bt) endotoxins, is the second most widely used trait (after herbicide resistance) in commercial genetically modified (GM) crops. Other modifications for insect resistance, such as proteinase inhibitors and lectins, are also being used in many experimental crops. The extensive testing on nontarget plant-feeding insects and beneficial species that has accompanied the long-term and wide-scale use of Bt plants has not detected significant adverse effects. GM plants expressing other insect-resistant proteins that have a broader spectrum of activity have been tested on only a limited number of nontarget species. Little is known about the persistence of transgene-derived proteins in soil, with the exception of Bt endotoxins, which can persist in soil for several months. Bt plants appear to have little impact on soil biota such as earthworms, collembolans, and general soil microflora. Further research is required on the effects of GM plants on soil processes such as decomposition. Assessment of nontarget impacts is an essential part of the risk assessment process for insect-resistant GM plants.

Animals↗

PubMed2000

Production and characterization of biologically active human GM-CSF secreted by genetically modified plant cells.

Human granulocyte-macrophage colony-stimulating factor (GM-CSF), a hemopoietic growth factor, was produced and secreted from tobacco cell suspensions. The GM-CSF cDNA was carried by a binary vector under the control of the CaMV 35S promoter and the T7 terminator. In addition, a 5'-nontranslated region from the tobacco etch virus (TEV leader sequence) was fused to the N-terminal end of the GM-CSF transgene. For ease of purification, a 6-His tag was added to the 3' end of the GM-CSF cDNA. Addition of the TEV leader sequence increased protein production more than twofold compared to non-TEV controls. Initial batch cultivation studies indicated a maximum of 250 microg/L extracellular and 150 microg/L intracellular GM-CSF. Western blot analysis detected multiple peptides with masses from 14 to 30 kDa in the extracellular medium. The plant-produced GM-CSF was biologically active and could be bound to a nickel affinity matrix, indicating that both the receptor-binding region and the 6-His tag were functional. The batch production of GM-CSF was compared with the production of other recombinant proteins secreted by transformed tobacco cells. The recovery of secreted GM-CSF was increased by the addition of stabilizing proteins and by increasing salt in the growth medium to physiological levels.

Blotting, Northern↗

PubMed2001

Molecular control of transgene escape from genetically modified plants.

Potential risks of gene escape from transgenic crops through pollen and seed dispersal are being actively discussed and have slowed down full utilization of gene technology in crop improvement. To ban the transgene flow, barren zones and 'terminator' technology were developed as GMO risk management technologies in transgenic crops. Unfortunately, the technologies have not protected reliably the transgene migration to wild relatives. The present study offers a novel molecular technique to eliminate gene flow from transgenic plants to wild relatives by recoverable block of function (RBF). The RBF consists of a blocking sequence linked to the gene of interest and a recovering sequence, all in one transformable construct. The blocking sequence blocks a certain molecular or physiological function of the host plant. Action of the blocking sequence leads to the death of the host plant or to an alteration in its phenotype resulting in inability for sexual reproduction in nature. The recovering construct recovers the blocked function of the host plant. The recovering construct is regulated externally by a specific chemical or physical treatment of the plants and does not act under natural conditions. In nature, hybrids of the transgenic plants with its wild relatives carrying the RBF will die or be unable to reproduce because of the blocking construct action. A working model of RBF is described in this report as one example of the RBF concept. This RBF example is based on barnase (the blocking construct) and barstar (the recovering construct) gene expression in tobacco under sulfhydryl endopeptidase (SH-EP) and a heat shock (HS) promoter, respectively.

Journal Article↗

PubMed2005

Risk mitigation of genetically modified bacteria and plants designed for bioremediation.

While the possible advantages of bioremediation and phytoremediation, by both recombinant microbes and plants, have been extensively reviewed, the biosafety concerns have been less extensively treated. This article reviews the possible risks associated with the use of recombinant bacteria and plants for bioremediation, with particular emphasis on ways in which molecular genetics could contribute to risk mitigation. For example, genetic techniques exist that permit the site-specific excision of unnecessary DNA, so that only the transgenes of interest remain. Other mechanisms exist whereby the recombinant plants or bacteria contain conditional suicide genes that may be activated under certain conditions. These methods act to prevent the spread and survival of the transgenic bacteria or plants in the environment, and to prevent horizontal gene flow to wild or cultivated relatives. Ways in which these genetic technologies may be applied to risk mitigation in bioremediation and phytoremediation are discussed.

Animals↗

PubMedDate not supplied

[Isolation of genetically modified potato plant containing the gene of defensive peptide from Amaranthus].

The plants of potato (Solanum tuberosum L., var. Desire) have been transformed with a pH22Kneo vector carrying the gene ac2, encoding the fungicidal peptide (defensin) from the seed of amaranth (Amaranthus caudatus L.). The transformation involved co-cultivation of potato stem explants (excised from aseptically grown plants) and Agrobacterium tumefaciens on solid MS medium. Factors affecting in vitro regeneration of the explants and the transformation efficiency were optimized. Regenerated potato plants harboring the amaranth defensin gene were selected by two traits, growth and ability to form roots on kanamycin-supplemented MS medium. The transgenic state was confirmed PCR analysis of ac2 in tissues of the kanamycin-resistant plants. The transgenic organisms thus obtained differed from the original ambiol-treated plants in growth patterns and proton translocation across the plasma membrane of the tuber cells.

Amaranthus↗

PubMed2005

Safety risks for animals fed genetic modified (GM) plants.

GM plants are widely grown all over the world, but many constraints still tend to discourage their use in Europe. Potential risks suggested to be associated with the use of GM are unexpected gene effects, allergenic potential, antibiotic resistance, gene flow. GM feed safety is presently evaluated by adopting the concept of GM substantial equivalence, by comparison with non-GM isogenic crops. Comparison is based on a wide spectrum of chemical components and on livestock performance. From the available experimental data, currently utilized GM plants appear safe and show no effects on animals or animal products. Hence, although they potentially exist, safety risks caused by the use of GM plants appear to be so low as be negligible in comparison with their potential benefits, if appropriately designed. GM plants represent a valuable option for future breeding, to increase yield while reducing the use of pesticides, improve plant adaptation to unfavourable environments, and produce better quality crops, also from a nutritional point of view. Nonetheless, GM crops are novel foods and the assessment of their safety using a scientific sound approach seems essential to protect the environment, as well as the health of humans and livestock.

Animal Feed↗

PubMed2006

Improved phytoaccumulation of cadmium by genetically modified tobacco plants (Nicotiana tabacum L.). Physiological and biochemical response of the transformants to cadmium toxicity.

The response of tobacco plants (Nicotiana tabacum L.)--non-transformed and transformed with a metallothionein gene MThis from Silene vulgaris L.--to increase cadmium supply in the nutrient solution was compared. The transgenic plants accumulated significantly more Cd both in the roots and the leaves. Visual toxicity symptoms and disturbance in water balance were correlated with Cd tissue content. Treatment with 300 microM CdCl(2) resulted in inhibition of photosynthesis and mobilization of the ascorbate-glutathione cycle. Treatment with 500 microM CdCl(2) led to irreversible damage of photosynthesis and oxidative stress. An appearance of a new peroxidase isoform and changes in the leaf polypeptide pattern were observed at the highest Cd concentration. The level of non-protein thiols gradually increased following the Cd treatment both in transgenic and non-transformed plants.

Antioxidants↗

PubMed2000

Compositional analysis of tubers from insect and virus resistant potato plants.

Genetically modified potato plants that are resistant to the Colorado potato beetle, plus either the potato leaf roll virus or potato virus Y, have recently been commercialized. As part of the safety assessment for plants produced by modern biotechnology, the composition of the food/feed must be compared to that of the food/feed produced by an equivalent plant variety from a conventional source. The composition of important nutritional and antinutritional factors in tubers produced by virus- and insect-resistant potato plants were compared to tubers produced by conventional potato plants. Key nutritional, quality, and antinutritional components measured were total solids, vitamin C, dextrose, sucrose, soluble protein, and glycoalkaloids. Proximate analyses included fat, ash, calories, total protein, and crude fiber. Minor nutrients measured were vitamin B6, niacin, copper, magnesium, potassium, and amino acids. The results from these analyses confirm that tubers produced by insect- and virus-protected varieties are substantially equivalent to tubers produced by conventional potato varieties.

Animals↗

PubMed2006

Invasion of pests resistant to Bt toxins can lead to inherent non-uniqueness in genetically modified Bt-plant dynamics: mathematical modeling.

Genetically modified crops are effective pest management tools for worldwide growers. However, there is a concern that pests may develop resistance to Bt-toxins produced by genetically modified Bt-plants. We study the impact of the Bt-resistant pests on Bt-crops. Furthermore, the dynamics of the Bt-plant-Bt-susceptible insects-Bt-resistant insects system is analysed and it is shown that throughout the insect reproduction period the plant biomass dynamics resulting from invasion of Bt-resistant insects is non-unique. Namely, the chaotic attractor and the limit cycle, which are responsible for the plant and insect biomass dynamics, are shown to coexist. As a result, the Bt-plant-Bt-resistant insect system can manifest either chaotic or regular oscillations of plant and insect biomass depending on spatial patterns resulting from invasion of Bt resistant insects into the Bt plant-Bt susceptible insect system. We show that the non-uniqueness of the system dynamics under unfavorable environmental conditions, such as in the so-called zones of risky agriculture in many developing countries and industrialized countries, can lead to essential decrease in the plant biomass.

Animals↗

PubMed1998

Biosafety of E. coli beta-glucuronidase (GUS) in plants.

The beta-glucuronidase (GUS) gene is to date the most frequently used reporter gene in plants. Marketing of crops containing this gene requires prior evaluation of their biosafety. To aid such evaluations of the GUS gene, irrespective of the plant into which the gene has been introduced, the ecological and toxicological aspects of the gene and gene product have been examined. GUS activity is found in many bacterial species, is common in all tissues of vertebrates and is also present in organisms of various invertebrate taxa. The transgenic GUS originates from the enterobacterial species Escherichia coli that is widespread in the vertebrate intestine, and in soil and water ecosystems. Any GUS activity added to the ecosystem through genetically modified plants will be of no or minor influence. Selective advantages to genetically modified plants that posses and express the E. coli GUS transgene are unlikely. No increase of weediness of E. coli GUS expressing crop plants, or wild relatives that might have received the transgene through outcrossing, is expected. Since E. coli GUS naturally occurs ubiquitously in the digestive tract of consumers, its presence in food and feed from genetically modified plants is unlikely to cause any harm. E. coli GUS in genetically modified plants and their products can be regarded as safe for the environment and consumers.

Ecology↗

PubMed2002

Foods as production and delivery vehicles for human vaccines.

Vaccination is a great asset for eradication of infectious diseases in humans and animals. With the prevalence of antibiotic resistant bacterial strains and an alarming increase in new and re-emerging pathogens, the need for vaccination continues to be a high priority for mammalian diseases. In the last several years, a novel approach for developing improved mucosal subunit vaccines has emerged by exploiting the use of genetically modified plants. It has been demonstrated that plant-derived antigens are functionally similar to conventional vaccines and can induce neutralizing antibodies in mammalian hosts. Using genetically engineered plants for the production of immunogenic peptides also provides a new approach for the delivery of a plant-based subunit vaccine, i.e., oral delivery, provided these immunogenic peptides are expressed in an edible part of the plant, such as grain or fruit. Thus, food crops can play a significant new role in promoting human health by serving as vehicles for both production and delivery of vaccines.

Communicable Disease Control↗

PubMed2006

Differences between lignin in unprocessed wood, milled wood, mutant wood, and extracted lignin detected by 13C solid-state NMR.

Solid-state 13C nuclear magnetic resonance (NMR) spectroscopy was applied to intact and isolated loblolly pine wood samples to identify potential structural changes induced by tree age, milling, lignin extraction, or naturally occurring mutations. Special attention was paid to ketone and aldehyde as well as nonpolar alkyl groups, which could be observed at low concentrations (<2 in 1000 C) using improved spinning-sideband suppression with gated decoupling. Carbonyl structures were present in intact wood, and there are more keto groups than aldehydes. Their concentrations increased from juvenile to mature wood and with milling time, whereas extraction did not alter the C=O fraction. Significant amounts of aldehyde and dihydroconiferyl alcohol residues were present in coniferyl aldehyde dehydrogenase-deficient wood, confirming solution-state NMR spectra of the corresponding lignin. These results demonstrate the utility of solid-state NMR as an assay for changes in the lignin structure of genetically modified plants.

Alcohols↗

PubMed2002

Lessons we can learn from ecological biosafety research.

The last decade has seen an increasing number of biosafety related publications focusing on transgenic organisms. Recent extensive field studies suggest that harmful laboratory effects on non-target organisms rarely occur in the environment. Moreover, biosafety studies typically show no difference in hybridisation between genetically modified plants (GMPs) or non-GMPs and related wild species. Since risk is a product of both exposure and hazard, biosafety research should clearly not only target gene flow exposure but specifically concentrate on expected hazards emerging from successful transgene flow to wild relatives of GMPs. Generally, transgenic plants behave in an ecologically similar manner to non-GMPs if the modified trait confers a neutral advantage under environmental or experimental conditions. However, GMPs perform better than non-GMPs if the new phenotype is challenged by conditions ecologically advantageous for the modified trait. Since biosafety research is a laborious process it will have to concentrate resources on thoughtful, thorough experiments, and target ecologically 'riskier' organisms. So far, we have no evidence that the use of GMPs contradicts sustainable agriculture and nature conservation per se.

Beta vulgaris↗

PubMed1996

Stability of food allergens to digestion in vitro.

An integral part of the safety assessment of genetically modified plants is consideration of possible human health effects, especially food allergy. Prospective testing for allergenicity of proteins obtained from sources with no prior history of causing allergy has been difficult because of the absence of valid methods and models. Food allergens may share physicochemical properties that distinguish them from nonallergens, properties that may be used as a tool to predict the inherent allergenicity of proteins newly introduced into the food supply by genetic engineering. One candidate property is stability to digestion. We have systematically evaluated the stability of food allergens that are active via the gastrointestinal tract in a simple model of gastric digestion, emphasizing the major allergens of plant-derived foods such as legumes (peanuts and soybean). Important food allergens were stable to digestion in the gastric model (simulated gastric fluid). For example, soybean beta-conglycinin was stable for 60 min. In contrast, nonallergenic food proteins, such as spinach ribulose bis-phosphate carboxylase/oxygenase, were digested in simulated gastric fluid within 15 sec. The data are consistent with the hypothesis that food allergens must exhibit sufficient gastric stability to reach the intestinal mucosa where absorption and sensitization (development of atopy) can occur. Thus, the stability to digestion is a significant and valid parameter that distinguishes food allergens from nonallergens.

Allergens↗

PubMed2001

Environmental risks of chemicals and genetically modified organisms: a comparison. Part I: Classification and characterisation of risks posed by chemicals and GMOs.

Risks can be characterised by several parameters. A risk is commonly defined to be the product of the extent of damage and the probability of its occurrence. But there are several other characteristics to be taken into account: degree of certainty in determining extent and probability, persistency, ubiquity, irreversibility, delay effect and mobilisation potential. As potential risks of genetically modified plants (GMPs), resistance to antibiotics, impact on non-target organisms, spread of genes and GMOs, and secondary consequences, e.g. on cultivation practice, are discussed in detail. Risks of GMPs are, in general, characterised by high uncertainty of the magnitude and probability of damage, a high mobilisation potential and a delay effect.

Environmental Pollutants↗